A brake unit of this kind is known, for example, from German patent application No. 2,545,542 published without examination. In the prior-art brake unit, the brakes associated with the driven wheels are preceded by a combination of two valves arranged in parallel and consisting of an electromagnetically actuatable valve and of a pressure-actuated valve. Only two switching conditions can be realized by this valve combination. In one switching condition, the brakes acting upon the driven wheels are connected to the brake pressure master unit in an unobstacled way. In the other, the hydraulic pressure existing in these brakes is limited in the event of a regenerative braking action, respectively of an emergency stop.
The fact that there is no possibility of recognizing the behavior of the electric driving motor and adapting the hydraulic portion of the brake power in an optimum manner to its characteristic is a disadvantage in the state-of-the-art brake unit.